Marking crabs

June, one of the NAPIRE students, measures and marks crabs (Allacanthos pitteiri) she’s caught with baited minnow traps. Her project has a lab focus too: she is investigating size and sex differences in coarse particulate organic matter (leaf) shredding behavior by presenting male and female crabs that vary in size with stream conditioned leaves and measuring how much they consume, or shred. This parallels a project another student performed in 2013, Joseph Jack, although Joseph varied leaf species and conditioning time.

Last year, Jerry studied predation risk in crabs and measured crab densities in stream pools. While he marked the crabs with nail polish as a mark-recapture method, the small labels June used have individual numbers (her mentor, Anne Brasher, brought them and has used them extensively with snails), which is a powerful tool.

An interesting observation: some of the crabs seemed to have rust-colored lesions on their carapace that look similar to lesions we often found on crayfish (Orconectes obscurus) caused by a chitin-eating bacteria, isolated (or at least studied) by Adam Leff’s lab at Kent State.